Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933945AbbELWbG (ORCPT ); Tue, 12 May 2015 18:31:06 -0400 Received: from e36.co.us.ibm.com ([32.97.110.154]:35474 "EHLO e36.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933141AbbELWbD (ORCPT ); Tue, 12 May 2015 18:31:03 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, Alexander Gordeev , "Paul E. McKenney" Subject: [PATCH tip/core/rcu 04/24] rcu: Panic if RCU tree can not accommodate all CPUs Date: Tue, 12 May 2015 15:30:34 -0700 Message-Id: <1431469854-3826-4-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <1431469854-3826-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20150512223034.GA1396@linux.vnet.ibm.com> <1431469854-3826-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15051222-0021-0000-0000-00000A7ACA82 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2266 Lines: 55 From: Alexander Gordeev Currently a condition when RCU tree is unable to accommodate the configured number of CPUs is not permitted and causes a fall back to compile-time values. However, the code has no means to exceed the RCU tree capacity neither at compile-time nor in run-time. Therefore, if the condition is met in run- time then it indicates a serios problem elsewhere and should be handled with a panic. Cc: "Paul E. McKenney" Signed-off-by: Alexander Gordeev Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 9b076b284695..f374f2caaf25 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -4087,16 +4087,19 @@ static void __init rcu_init_geometry(void) rcu_capacity[i] = rcu_capacity[i - 1] * CONFIG_RCU_FANOUT; /* + * The tree must be able to accommodate the configured number of CPUs. + * If this limit is exceeded than we have a serious problem elsewhere. + * * The boot-time rcu_fanout_leaf parameter is only permitted * to increase the leaf-level fanout, not decrease it. Of course, * the leaf-level fanout cannot exceed the number of bits in - * the rcu_node masks. Finally, the tree must be able to accommodate - * the configured number of CPUs. Complain and fall back to the - * compile-time values if these limits are exceeded. + * the rcu_node masks. Complain and fall back to the compile- + * time values if these limits are exceeded. */ - if (rcu_fanout_leaf < CONFIG_RCU_FANOUT_LEAF || - rcu_fanout_leaf > sizeof(unsigned long) * 8 || - n > rcu_capacity[MAX_RCU_LVLS]) { + if (n > rcu_capacity[MAX_RCU_LVLS]) + panic("rcu_init_geometry: rcu_capacity[] is too small"); + else if (rcu_fanout_leaf < CONFIG_RCU_FANOUT_LEAF || + rcu_fanout_leaf > sizeof(unsigned long) * 8) { WARN_ON(1); return; } -- 1.8.1.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/